Changes in the Security Environment Surrounding Japan
Shifting Power Balance and the Three Front Threats Posed by China, North Korea, and Russia

Ken Jimbo


The premise for deciding Japan's national security strategy and defense strategy is to understand the characteristics of the security environment surrounding Japan. At a meeting of the "Advisory Panel to Comprehensively Discuss Defense Capabilities as National Strength," General Ryoichi Oriki, former Chief of the Joint Staff Office, expressed his recognition that "Japan is facing one of the great postwar difficulties." 1 As summarized in this expression, it is the almost unanimous government-wide view that the security environment of Japan is demanding.

In this context, we need a dynamic insight into the characteristics comparing the past with the present "severe security environment" and also into how it will evolve into the future. This perception will provide the basis for judging whether the level of defense capabilities should be raised while fundamentally maintaining the conventional strategy (qualitative changes in threats are small, but quantitative changes are large) or whether the conventional strategy should be changed and defense capabilities drastically reinforced (both qualitative and quantitative changes in threats are large).

This paper argues that Japan's security environment has changed significantly from the past, both qualitatively and quantitatively, which requires a shift in Japan's defense strategy and a drastic reinforcement of its defense capabilities. To this end, it begins with discussing how the balance of power in the Indo-Pacific region is changing, the security threats that Japan faces, the role that Japan's defense forces should play, and changing priorities in reinforcing defense capabilities.

The Balance of Power in the Indo-Pacific

The impact on Japan's security of superpower relations in the Indo-Pacific region is the most significant structural factor to focus on. DEFENSE OF JAPAN 2022 begins with the characteristics of the contemporary security environment stating that "changes in the balance of power are accelerating and becoming more complex. In addition, uncertainty over the existing order is increasing." 2 This shift in power balance is driven by China's growing national power.

The following table shows the defense expenditures (in US dollars and nominal values) of the United States, China, India, ASEAN-6 (Singapore, Thailand, the Philippines, Malaysia, Indonesia, and Vietnam), Japan, and Australia, based on the Stockholm International Peace Research Institute (SIPRI) military expenditure database. 3 The figures are calculated by using each country's recent five-year average ratio of defense expenditures to GDP, based on the medium-term forecasts in the IMF's World Economic Outlook (October 2022) for the years 2025 and 2030.

The US defense spending is announced to be $778.397 billion for 2020 and $800.672 billion for 2021; it is expected to reach $855.028 billion for 2025 and $1.7837 trillion for 2030. China's defense spending is announced to be $257.973 for 2020 and $293.352 for 2021. If applying the same calculation formula, it will sharply rise to $427.147 for 2025 and $612.127 for 2030. China's defense spending as of 2030 is estimated to account for about 60% of that of the United States.

In 2005, the US defense/GDP ratio was about 12 times higher than China's by an overwhelming margin. Not only that, but Japan's defense/GDP ratio was 1.03 times higher than that of China, or almost on par, while the same power index for other Asia Pacific countries in comparison with China's were: India (54%), South Korea (52%), ASEAN (35%), and Australia (31%).

In 2020, however, Asia Pacific countries' defense/GDP ratio compared with that of China rapidly dropped: Japan (19%), India (31%), South Korea (18%), ASEAN (18%), and Australia (11%). As for 2030, the estimations will be as follows: Japan (12%), India (26%), South Korea (11%), ASEAN (14%), and Australia (7%). Noteworthy is the case of Taiwan; its defense/GDP ratio compared with China's is predicted to decline from 19% to 5% to less than 5% during the period from 2005 to 2020 to 2030. The US defense spending for 2030 will still be 1.6 times the size of China's. But other Asia Pacific countries' relations with China will show an essentially different vista.

Table 1. Trends of Defense Spending of US, China, ASEAN, Japan, and Australia
Unit: 1 million dollars (current USD)

2010 2015 2020 2025 2030
The US 738,005 633,829 778,397 855,028 1,007,837
China 105,523 196,539 257,973 427,147 612,127
India 46,090 51,295 72,937 109,174 160,868
ASEAN6 26,699 35,134 45,942 60,663 83,701
Japan 54,655 42,106 51,970 (57,160) (64,421)
Australia 23,217 24,046 27,301 35,688 44,335

Source: Projections based on SIPRI Military Expenditure Database (2021)*
*Figures for and after 2025 were calculated based on the following estimations: U.S. (3.2%), China (1.9%), India (2.6%), ASEAN (1.4%), Japan (0.9%), and Australia (1.85%)

The "long-term strategic competition" between the United States and China is considered to be China's relatively slow-paced challenge to medium- to long-term US supremacy. From the US perspective, China's rise is viewed as a systemic catch-up effort against the US national power.

For Asia Pacific countries, however, the shift in the balance of power with China should be considered a short-term, rapid change. In particular, although Japan's defense spending had exceeded China's until 2005, the relationship has changed rapidly in just 25 years, and Japan's defense spending will likely fall to one-tenth of that of China by 2030. The changing power balance in Japan-China relations should be understood to be something of the scale that the bilateral relationship on par transforms into that in favor of China with the ratio of one versus ten in 25 years.

Japan's Defense Policy and Challenges for the Japan-US Alliance

This power shift will bring about a structural change in the strategic environment in East Asia. Until the early 2000s, the East Asian strategic environment had been assumed to be a situation where the United States had overwhelming dominance over China and Japan alone could secure air and maritime superiority over China. It was possible to maintain the Japan-US alliance and to shape Japan's defense policy under the assumption that the United States and Japan could remain superior to China in their respective relations with the latter.

Since the 2010s, however, China's "anti-access/area denial" (A2/AD) capabilities against the United States have expanded, and the United States has had to envisage a strategic environment in which the supremacy of US forward-deployed forces is not unconditional. Even though the US military outperforms the Chinese military in terms of conventional forces and operational capabilities, it has become difficult for the United States to maintain strategic superiority in the Western Pacific; the estimated cost of military intervention in contingencies in the Taiwan Strait and South China Sea has risen significantly.

In Japan-China relations, not only is it very hard for Japan to deter China on its own, but it is also becoming even harder to maintain an autonomous capability in the staged crisis management (escalation management). The National Defense Program Guidelines (December 2018) envisaged a harsh situation "when maintaining maritime and air superiority becomes untenable." Such a situation will undoubtedly become even graver.

Amid this power shift, China is stepping up its offensive against neighboring countries. In the East China Sea, it has made maritime advances into the waters surrounding the Senkaku Islands; in the South China Sea, it is constructing artificial islands and militarizing the area; it is also increasing military pressure on Taiwan. Former US Indo-Pacific Command Commander Davidson's statement at a Senate Armed Services Committee hearing that China could invade Taiwan "in the next six years" may suggest that China will likely become more confident of its ability to invade Taiwan in the late 2020s while preventing US military intervention. 4

The power shift in the Indo-Pacific region will also change the dynamics of alliance management between the United States and its allies. As the allies will reduce their capabilities of addressing crises with China by themselves, they will increasingly seek US military commitment and intervention even in small- and medium-scale conflicts. It is a reflection of possible changes in the dynamics that, in the management of the Japan-US alliance, the application of Article 5 of the Japan-US Security Treaty to the Senkaku Islands issue has been repeatedly confirmed. US-Philippine joint defense of the islands that the Philippines effectively controls in the South China Sea is an overriding agenda for the US-Philippines alliance.

Yet, US military involvement in small- and medium-scale conflicts facing these allies does not always enjoy support at home. As the cost of US intervention in those conflicts with China is supposed to increase, if US allies become more dependent on US defense cooperation without securing sufficient defense budgets, the dissatisfaction of the American public with their allies will increase. Behind the former Trump administration's strong dissatisfaction with the level of defense spending of European countries and its demand for a sizable increase in the cost of stationing US forces in South Korea was its frustration that the allies fail to "share a fair burden."

This latent US discontent with weak alliance management should be considered present in the Biden administration that emphasizes alliance relations. The Japanese side tends to base its evaluation of US-China policy on how much of a hardline stance the US administration takes and, therefore, how much it evaluates the Japan-US alliance. On the other hand, the US side emphasizes what autonomous responsibilities Japan fulfills. In this context, it is imperative for Japan to fundamentally strengthen the defense of the Senkaku Islands and other remote islands, as well as its defense posture in the East China Sea and the Nansei Islands.

The Japan-US alliance's commitment to the US-China relationship in the power shift will be in full swing. Specifically, the focus will rest on the defense of Taiwan and the alliance's response to the deployment of Chinese forces across the First Island Chain. Following the Guidelines for Japan-US Defense Cooperation (April 2015), the allies have examined the nature of a joint Japan-US response in the low-end domain (gray zone situations), primarily with the Senkaku Islands in mind. However, Japan-US defense cooperation in the high-end one is necessary for the defense of Taiwan and wide-area defense. Defense cooperation in this area requires a defense posture of a completely different dimension in terms of strategicity, more sophisticated theaters of operations, and necessary accuracy and precision in joint operations.

The basic guidelines for Japan-US defense cooperation in the high-end domain aim to ensure the forward deployment of US forces in the Western Pacific even under an A2/AD environment and to deploy state-of-the-art strike assets of the US Navy and Air Force, thereby maintaining a posture enabling the US Marine Corps to deploy in rapid response. Assuming a Taiwan contingency and wide-area deployment of the JSDF, Japan must see to it that the JSDF can enhance Japan-US joint operational capabilities in a high-end environment. The allies must also ensure that US bases in Japan can effectively function as force projection platforms and develop their resilience to quickly restore the functions if attacked.

Furthermore, assuming a situation in which Japan is unable to maintain effective maritime and air superiority over China and the US military is also unable to secure operational access to the Western Pacific, the allies should earnestly develop assets that enable standoff attacks as an offensive capability from "outside the threat zone." Wide-area defense on Japan's Pacific side, the expeditionary capabilities of maritime assets, and long-range transport capability should be positioned as force re-projection into the theater in a contingency.

The Three Front Threats from China, North Korea, and Russia

A distinctive feature of the contemporary security surrounding Japan is that the country is obliged to simultaneously deal with three military powers: primarily the military capabilities of a rising China, then, North Korea's persisting development of nuclear weapons and missiles, and Russian military developments in the Far East. The problem is that China, North Korea, and Russia have different military capabilities, making it hard for Japan to address them following the same policy. If Japan were to adopt the approach of building up its defense capabilities against China, North Korea, and Russia separately, it would be heavily burdened with efforts to work out the force composition of the JSDF and the necessary defense capabilities to deal separately with them. If the three countries deepen military alignment on the China-Russia, China-North Korea, or Russia-North Korea basis, the burden on the JSDF's operational planning will further increase due to their mutual operational coordination and diversionary operations.

Here, too, we should note changes in the situation. The National Security Strategy (December 2013) and the National Defense Program Guidelines for FY2019 and Beyond assess China, North Korea, and Russia in association with Japan's security, as shown in Table 2. 5

Table 2. A Comparison of Statements Related to China, North Korea, and Russia in the 2013 NSS and the NDPG for FY2019 and Beyond

National Security Strategy (2013) NDPG for FY2019 and Beyond

1. Such an external stance and military activities by China, coupled with a lack of transparency in its military affairs and security policy, have become an issue of concern to the international community including Japan; therefore, the Government of Japan needs to pay careful attention to this situation.

2. Stable relations between Japan and China are an essential factor for peace and stability of the Asia-Pacific region. From a broad, as well as a medium- to long-term perspective, Japan will strive to construct and enhance a Mutually Beneficial Relationship Based on Common Strategic Interests with China in all areas, including politics, economy, finance, security, culture and personal exchanges.

1. China engages in unilateral, coercive attempts to alter the status quo based on its own assertions that are incompatible with existing international order. In the East China Sea and other waters, China is expanding and intensifying its military activities at sea and in the air.

2. Such Chinese military and other developments, coupled with the lack of transparency surrounding its defense policy and military power, represent a serious security concern for the region including Japan and for the international community. Japan needs to continue to pay utmost attention to these developments.

DPRK North Korea's ballistic missiles development, including those with ranges covering the mainland of the U.S., along with its continued attempts to miniaturize nuclear weapons for warheads and equipping them to ballistic missiles, substantially aggravate the threat to the security of the region, including Japan.

1. Given technological maturity obtained through a series of nuclear tests, North Korea is assessed to have already successfully miniaturized nuclear weapons to fit ballistic missile warheads.

2. Such military developments of North Korea pose grave and imminent threats to Japan's security and significantly undermine peace and security of the region and the international community.

Russia It is critical for Japan to advance cooperation with Russia in all areas, including security and energy, thereby enhancing bilateral relations as a whole, in order to ensure its security. Russia is enhancing its military posture by continuing force modernization efforts with a focus on nuclear forces. Russia is in sharp confrontation with Europe and the United States over issues including situation in Ukraine. Russia's military activities are trending upward in the Arctic Circle, Europe, areas around the United States and the Middle East, as well as in the Far East including Japan's Northern Territories. Close attention therefore needs to be paid to its developments.

Source: Cabinet Secretariat, "On the National Security Strategy" and "On the National Defense Program Guidelines for Fiscal Year 2019 and Beyond" (December 18, 2018)

Regarding these assessments, it is necessary to understand quantitative and qualitative changes related to China, North Korea, and Russia as of 2022. First, China's military expenditures; land, sea, and air power; capabilities for electronic warfare/cyber/space domain; and joint operations capabilities have all significantly improved. These developments in capabilities have not only further strengthened China's A2/AD capabilities against US forces but also heightened the reality of its ability to invade Taiwan and have opened a new phase for the country, including the acquisition of sustainable maritime air superiority in the South China Sea. These developments account for the necessity on the allies' side of more high-ended preparedness in the US military posture in the Western Pacific, the Japan-US alliance's joint operational planning, and the JSDF's defense posture.

The National Security Strategy (2013) states that "Stable relations between Japan and China are an essential factor for peace and stability of the Asia-Pacific region" and calls for strengthening "mutually beneficial strategic relations" between Japan and China. This is based on the idea of controlling tensions in Japan-China relations and extending mutual benefits based on Japan's trade with and direct investment in China and the economic interdependence between the two countries.

Nonetheless, the Japanese government's recent political assessment of China has been unfavorable to it because of the following factors: the introduction of Hong Kong's National Security Law in 2020, human rights issues in Xinjiang and with the Uyghurs, repeated incursions by Chinese official vessels into the waters surrounding the Senkaku Islands, China-Russia military exercises in areas surrounding Japan, and the increasing concentration of power by President Xi Jinping at the 20th CPC Party Congress. The enforcement in Japan of the "Economic Security Promotion Law" has led to warnings against excessive dependence on the Chinese market, export controls on cardinal technologies, and restrictions on investments by the Chinese. There is growing momentum to review Japan-China economic interdependence. In light of these trends, Japan's security strategy toward China will surely place more emphasis on "strategic competition."

Second, North Korea's nuclear and missile development poses a serious and imminent threat to Japan's security. Regarding the current status of North Korea's nuclear weapons program, DEFENSE OF JAPAN 2022 assesses that "…given the technological maturity obtained through a series of nuclear tests, North Korea is assessed to have already miniaturized nuclear weapons to fit ballistic missile warheads." Assuming a North Korean ballistic missile attack as a nuclear attack requires more effective deterrence against North Korea and the development of ballistic missile defense. It will be necessary to maintain a system of extended deterrence by nuclear and conventional forces under the Japan-US alliance and to develop missile defense.

North Korea's nuclear missiles are making rapid progress: they have acquired longer ranges, adopted more diverse launch modes, and improved operational accuracy and capability required for saturation attacks, as well as secrecy and immediacy. Moreover, they boast an upgraded surprise attack capability. Since March 2021, North Korea has, as part of its diversification of missile capabilities, been testing the launch of a low-altitude irregular trajectory missile allegedly employing technology employed in Russia's Iskander. Such a missile that would neutralize missile defense of target countries has the effect of making their defense efforts costly.

North Korea's successful development of ICBMs has made its ability to conduct a direct attack on the US mainland appear as a real scenario. If North Korea were to acquire the capability of conducting a nuclear strike against the United States, it might be induced to launch a preemptive strike against or be obliged to adopt a compromising policy toward North Korea.

The problem found here is the decoupling of the alliance. Imagine a scenario where the United States launches an attack on North Korea; North Korea resorts to military retaliation against South Korea and Japan, causing tremendous damage. Could the alliance address such a worst-case scenario? Or, if the United States agreed to assure North Korea's security in exchange for dismantling its long-range missiles with a range reaching the US mainland, would Japan conclude that the United States has abandoned an allied Japan?

Furthermore, if the United States feels threatened by nuclear attacks from North Korea, will it not be obsessed with the idea of sacrificing the US mainland by defending Japan? As a result, will extended deterrence not lose credibility? Then, if North Korea unilaterally concludes that it has gained deterrence capability against the United States, will the North, believing US military intervention to be difficult, not activate localized military actions? Such sequential thinking concerning decoupling will cast light on important issues.

Thirdly come fundamental changes in Russia's positioning. The National Security Strategy (2013) states, "It is critical for Japan to advance cooperation with Russia in all areas, including security and energy, thereby enhancing bilateral relations as a whole, to ensure its security." Afterward, Japan and Russia endeavored to foster trust through the establishment of Japan-Russia Foreign and Defense Ministerial Consultation ("2+2" Ministerial Meeting), mutual visits by defense ministers, and enhanced defense exchange (including Japan-Russia joint search and rescue training). Although Russia deepened tensions with Western countries over its invasion of Crimea in 2014 and its intervention in the Syrian civil war in 2015, Japan tenaciously endeavored to maintain stable relations with Russia. Undoubtedly, the Japanese government had the political will to resolve the Northern Territories issue through the conclusion of a Japan-Russia Peace Treaty.

Japan's quest for stable relations with Russia included another strategic element. The thinking was that it was vital to stabilizing relations with Russia to face China, the overriding challenge to Japan's security. 6 When competitiveness and confrontation deepen in US-China and Japan-China relations, if Russia strengthens its alignment with China, Japan's security environment will considerably deteriorate. It would be difficult to alienate Russia and China, but it may be possible that Japan-Russia relations will help disperse Russia's strategic interests in Asia. Positioning Japan-Russia economic relations and Japan-Russia peace treaty negotiations in this way would allow us to seek strategic interests beyond the solution of the Northern Territories issue.

However, Japan had to fundamentally change this strategic positioning of Japan-Russia relations due to Russia's invasion of Ukraine in February 2022. Following the Russian invasion of Ukraine, the Japanese government strongly condemned Russia and, together with Western countries, implemented comprehensive economic sanctions against the country. In March 2022, Russia announced that it would suspend Japan-Russia peace treaty negotiations and withdraw from the dialogue on joint economic activities in the four northern islands, criticizing Japan for "anti-Russian behavior." Since then, there has been no sign of improvement in Japan-Russia relations.

These changes in Japan-Russia relations signify that Russia can develop its policy toward Japan in the Far East without considering its economic relationship with Japan or bilateral peace treaty negotiations. Due to the difficulty in alienating Russia and China over their interests, China-Russia military alignment will supposedly further develop. The Russian and Chinese militaries are promoting concerted actions in the air and maritime space around Japan. As early as 2019, Russian Tu-95 strategic bombers and Chinese H-6 bombers flew joint flights from the Sea of Japan to the East China Sea as part of the "China-Russia joint aerial strategic patrol." Another joint flight took place in May 2022 after the Russian invasion of Ukraine. During the "Vostok-2022" in September 2022, the Chinese and Russian navies conducted a large-scale joint exercise in the Sea of Okhotsk and the Sea of Japan.

The current progress in China-Russia military relations is deeply associated with their shared strategic interests. Russia and China appear to seek to counter US military power in the Western Pacific and to disrupt the Japan-US alliance. In the event of a Taiwan contingency, Russia's deployment of military forces and alignment with China would complicate operational planning by the United States and Japan. Russia's buildup of its Far Eastern forces (including missile deployment) and expansion of military activities would have a significant impact on the JSDF's posture, operational planning priorities, and reform direction. For example, if the JSDF is forced to allocate more resources to Japan's northern defense, the situation may effectively delay the JSDF's southwestern shift designed to address China's movements in that direction. Japan's national security strategy must face Russia as a cost imposer and spoiler.

Priorities in Japan's Defense Reinforcement

In the past, the National Defense Program Guidelines presented basic ideas of Japan's defense capabilities. For example, the NDPG for FY2019 and Beyond aims to build a "multi-domain defense force," which is described as "a truly effective defense capability" that "organically fuses capabilities in all domains including space, cyberspace, and electromagnetic spectrum." The document also enumerates the "roles that defense capability should play," which include response to situations ranging from peacetime to gray zone, island defense, response to new domains, response to large-scale disasters, collaboration with the United States based on the Japan-US alliance, and the promotion of security cooperation.

What has been listed above can be understood as broadly indicating major items associated with the changes in the military situation surrounding Japan, the role that the JSDF should play, and the JSDF's posture. However, it is hard to extract judgment from the list on what levels of quality and quantity of defense capabilities are necessary for Japan's security; how much defense expenditures and resources will be required to meet those levels; what item should be prioritized if all levels cannot be met; how relationships and role-sharing with the allies and like-minded countries should be decided. To discuss these issues, it is vital to present a "strategy" that goes beyond the concept of defense buildup or the presentation of the roles of defense capabilities.

The following are some proposals on what strategy Japan should adopt, based on what this essay has so far discussed: the changes in the balance of power surrounding Japan, China's military rise as a systemic change, and the three-front threats posed by China, North Korea, and Russia.

First, in an environment where the expansion of China's military power and China's maritime and air superiority is irreversible, it is no longer possible to position Japan's defense capabilities as a quantitative balance with China (= the required defense capabilities based on the balance of power). Therefore, increasing the number of 5th-generation fighter jets or procuring large-sized destroyers as a quantitative balance is impossible, given the disparity in defense expenditures between Japan and China. A return to the concept of "basic defense capabilities," according to which Japan should possess the minimum defense capabilities necessary to respond to a limited, small-scale landing invasion without becoming a power vacuum, could not be valid in the current severe security environment. It is vital to present a strategic theory that goes beyond the strategies that form the basis of the above concepts of required defense and basic defense capabilities.

In a strategic environment where Japan's inferiority to China has been fixed, the most effective strategy Japan should take is a denial strategy, which, through an assessment of the theory of victory by which a country of concern attempts to change the status quo by force, "denies" that country "the ability to conduct operations." 7 Given the phased development of contemporary crises, the passage of time, and the ability to project military forces, the strategy in question should be defined as a "theater denial strategy" capable of denying the adversary the ability to conduct operations at a greater distance. This strategy differs from "deterrence by punishment" that inflicts unsustainable damage on an adversary to form a deterrent force. Even in a situation where there is a significant power gap in favor of the adversary, the theater denial strategy aims to build the capability to deny the adversary the success of its operations to change the status quo. To implement this strategy with greater strategic depth, a long-range strike capability (the counterstrike capability currently advocated by the Japanese government) will be the key.

Second, it is desirable to assess potential threats and their nature and to work out crisis scenarios and operational plans to address each of the three fronts (China, North Korea, and Russia), and that the posture of the JSDF should be developed accordingly. However, with the limited financial and human resources, it is uncertain whether it is possible to create a comprehensive posture capable of simultaneously conducting operations on the three fronts. Then, the Japanese government should prepare and develop versatile equipment and operational plans that could be effective for all the three countries. To be specific, efforts to this end include: ground-based radar coverage, a warning and surveillance posture based on satellite information, missile defense with wide-area response capabilities, troop formation with high mobility and deployment capabilities, and the active introduction of unmanned systems.

Third, the Japan-US alliance and the alignment with like-minded countries should be linked with the "theater denial strategy." Due to the rapid reinforcement of China's air and naval forces, ballistic/cruise missile strike capabilities, and cyber/electronic warfare capabilities, the US military deployed in Asia is facing the problem that the supremacy of US forward-deployed forces and force projection capabilities is becoming less apparent. Under these circumstances, Japan's alliance strategy must ensure the forward deployment of US forces even in an A2/AD environment and strengthen Japan-US joint operations. It is necessary to deploy the most advanced strike assets of the US Navy and Air Force to the Western Pacific theater and to maintain the readiness of the US Marine Corps for immediate deployment. To this end, it is important to enhance the survivability of US military facilities and premises in Japan and to create a system that allows for joint use of the JSDF facilities and flexible use of civilian airports and port/harbor facilities. It is also necessary to work with Australia, South Korea, the Philippines, and Singapore to hasten to establish a posture to support the US military presence in the region.


This paper has examined the characteristics of the security environment of Japan from the perspective of the shifting power balance and the three front threats posed by China, North Korea, and Russia and has discussed the direction that Japan's defense strategy should take. As it has shown, the security environment surrounding Japan is undergoing a structural shift that cannot be understood merely as an extension of the past structure. In particular, this paper emphasizes that China's military power has created a situation where US theater supremacy is not unconditional while it is difficult for Japan to secure maritime and air superiority. This situation cannot be discussed from the perspective of the strategy formulated in the days when the United States and Japan were dominant in Asia.

This paper has also discussed that China, North Korea, and Russia—each presenting different security challenges—are acting together to impose more costs on Japan. The Japanese government once attempted to alienate Russia from the other two countries while promoting Japan-Russia relations on the political and economic fronts. Russia's invasion of Ukraine made this Japanese policy line untenable. Meanwhile, Japan cannot face the three countries in the same manner and simultaneously. If a hold-hold-deter-and-response strategy could be formulated by which to hold the actions of Russia and North Korea and to deter and respond to China, it might be desirable. Yet, as China, North Korea, and Russia explicitly and implicitly deepen strategic alignment, it is becoming increasingly hard to draw such a simple picture.

The main thrust of this paper is that in this strategic environment, Japan should take an active role in promoting its security and regional stability while pursuing a "theater denial strategy.

(Professor, Keio University)

(Translation by Tsutomu Inuzuka)

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